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Continuous Tone-Coded Squelch System or CTCSS is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel like UHF CB and is quite often referred to as tone squelch .
Where more than one user group is on the same channel, CTCSS filters out other users if they are using a different CTCSS tone or no CTCSS.
Instead of turning on the receive audio for any signal, the two-way
radio receiver's audio turns on only in the presence of a signal AND
the correct tone.
A carrier squelch or noise squelch
receiver is unlocked and will let any signal in. A receiver with CTCSS
locks out all signals except ones encoded with the correct tone.
Following is a list of the common CTCSS Code Numbers and Frequency
|
Code Number |
Frequency (Hz) |
Code Number |
Frequency (Hz) |
oF
|
OFF |
20 |
131.8 |
|
1 |
67.0 |
21 |
136.5 |
|
2 |
71.9 |
22 |
141.3 |
|
3 |
74.4 |
23 |
146.2 |
|
4 |
77.0 |
24 |
151.4 |
|
5 |
79.7 |
25 |
156.7 |
|
6 |
82.5 |
26 |
162.2 |
|
7 |
85.4 |
27 |
167.9 |
|
8 |
88.5 |
28 |
173.8 |
|
9 |
91.5 |
29 |
179.9 |
|
10 |
94.8 |
30 |
186.2 |
|
11 |
97.4 |
31 |
192.8 |
|
12 |
100.0 |
32 |
203.5 |
|
13 |
103.5 |
33 |
210.7 |
|
14 |
107.2 |
34 |
218.1 |
|
15 |
110.9 |
35 |
225.7 |
|
16 |
114.8 |
36 |
233.6 |
|
17 |
118.8 |
37 |
241.8 |
|
18 |
123.0 |
38 |
250.3 |
|
19 |
127.3 |
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Channel & Frequency Information 
